The invention relates to a method of manufacturing glass bodies, in which the starting material for the glass body, being an anhydrous suspension having a microdispersed solids content, is used to form a porous green body which is subsequently purified and sintered.
The invention further relates to arrangements for carrying out such a method as well as to the use of the glass bodies manufactured by the method in accordance with the invention.
The method mentioned in the opening paragraph is particularly suitable for the manufacture of quartz-glass preforms for optical waveguides.
For the manufacture of very pure quartz-glass bodies, particularly preforms for optical waveguides, methods are known in which a porous green body is manufactured from microdispersed SiO.sub.2 glass particles, after which the said green body is first purified in, for example, a chlorine-containing atmosphere at temperatures ranging from 600.degree. to 900.degree. C. Next, the green body is sintered at a temperature of approximately 1500.degree. C. to form compact and transparent glass; the sintering temperature depends on the size of the SiO.sub.2 particles and the homogeneity of the green body.
Processing of microdispersed quartz-glass particles involves a substantial investment in equipment, preforms for the manufacture of a green body which is easy to manipulate and presses to compact this green body in order to obtain a green body having a density which is so high as to enable an efficient sintering process, i.e. sintering at temperatures .ltoreq.1550.degree. C. to form a glass body which is free from bubbles and reams. Such a method for the manufacture of a preform for optical waveguides is known from, for example, DE 3240335.
In order to produce green bodies having a sufficiently high density, microdispersed SiO.sub.2 suspensions which are deformed into a green body may alternatively be used. DE 2925309 describes a method in which an SiO.sub.2 suspension is sprayed in or on a carrier tube. A disadvantage of this method is that high demands are made on a uniformly operating spraying device and that the green body obtained cannot be purified in a hot gas atmosphere which reacts with the impurities because the carrier tube is not porous.